Apparatus for recutting helicoidal gears



Euy 23, 1935.' w. F. ZIMMERMANN APPARATUS FOR RECUTTING HELICOIDAL GEARS Filed April 16, 1952 4 Sheets-Sheet l Clllflllllilllllllllllll 4 SheetS-Slheet 2 w. F. ZIMMERMANN APPARATUS FOR RECUTTING HELICOIDAL GEARS July 23, 1935.

Filed April 16, 1952 July 23, 1935.- w, F. ZIMMERMA'NN 2,008,140

APPARATUS FOR RE'SCUTTING HELICOIDAL GEARS Filed April 1e, 1932 4 sheets-sheet 5 INVENTOR- lma 1" I I WMZZM, W

ATTORN July 23; 1935. w. F. ZIMMER'MANN APPARATUS FOR RECUTTING HELICOIDAL GEARS Filed April 16, 1952 4 Sheets-Sheet 4 -INVENTCR- I ATTQRNE s n Patented July 23, 1935 VV.GEARS` william F. zimmermanngmepitvooa, N; 3J., as-

signor to Gould & Eberhardt; Newark, N. J., a

corporation of `NewfJersey y Appiicationspru "16, 1932, Seriai Naoasn 14 claims. Y

, Thisinvention is directed to a method forrecutting helicoidal gears andan apparatus capableof effecting such method.

. Despite certain recognized advantages of heli- 5 cal gearing itsuse in the past has been considerably curtailed by the inability onthe part of manufacturers to commercially and-economically produce helical gears which would operate with satisfactory quietness. Witness, for examplathe l fact that many manufacturers of auto engines Vhave found it preferable to employ a chain and sprocket drive ratherthan intermeshing helical gears for the timing gear drive; or have resorted.

to such expediente. as the interposition in the gear train` of a non-metallic gear, all primarily in the interests of quietness and smoothness of operation.

Thepresent invention is of especial importance in the manufacture of certainjtypes of imv 20` proved auto transmissions, such asthe synchromesh, employing helical gears in which environ` ment the degree of quietness is. of the utmostw importance. vThe invention is further important in its eiectuation of economies, it being a primary object to greatly reduce vthe manipulations and time consumed in the complete operation of Y producing the gear teeth; while at .the same time attaining an uniformity of tooth'spacing.

and correctness of tooth form suiiiciently accu- 30` rate to satisfy the most exacting requirements in commercially employed gears; Y As aV fundamental of gear cutting `it may beV noted that it is practically impossible -to corn-V merciallyprcduce a gear from av nislied lblank r in a single cutting operation, which gearadf heres sufficiently close to the specica'tionsfdS to be satisfactory for such usesas thosereierred to. .Itkhas been vfound necessary, therefore, to

first cut the gear spacesY to the approximate size,` andfollow this with a light nishing operation.

As a practical matter, however, the finishing or re-cutting of ,helicoidal gears on a largescale has 'presentedea diiicultpro-blem. 4vThe desired' standards of accuracy and iinish vare obtained'L whenv there is but .005 to .010 inch of metal to be removed from the tooth sides. -To remain'with in therlimits of allowance, wherein somey Vmetal is removed over the entire to'oth prole-as' the -hob cutter teeth progress down the helical grooves of the gear, but at no point causing the hobto be burdened with .the takingA oimore than ,a light cut, requires an initial settingof"v the -hob and gear blanks and the inai'it'enancey 55 0i @een demie. relations,iheiiryellestrdeuaf (ci. gio-e4) tion vfrom'whichlwould result an inaccuratev y gear-within the standards desired.

Due jto the diculty heretofore experiencedV in establishing asuiciently accurate set-up, oncev the gear fblankshave been removed from' the 5'- arbor upon which they were rough-cut, various methodslflave ,been `developed and employed for re-cutting helical gearson the same machine atVV the completion` of the'roughing operation retaining the same setting of Wthe gearblanks on their spindle. y These methods have varied considerably dependent inglarge part upon the typerof rnachine andthe adjustments which individual in-v ventors have been, able to develop and apply thereto.` .A Y

Aside'frorn the fact, however, that these prior methods require the exerciseA of considerablel skill,and are, in many instances, time-consuming andineicient; they are subject to a further and. major, disadvantage of being impractical in attempting rto intermittently utilize thel same machineand cutter forboth roughingand finishingom-nations.y ln accordance with the present invention the gear blanks may lbe ,roughed out with a roughng hob on any type of machine vv designedto withstand the severe operating conditionsattendant upon the initial and major cut. lIhe roughedl out blanks are then set up and recut on au precision machine equipped with an respecially accurate hob. Under the relatively less strenuous conditions of the re-cutting operation the re-cutting machine and its hob may bemaintained in superior conditiony resulting in exceptionally accurate` uniform helical tooth spaces and anne smooth nish. The resultant is Anotonly an improvement in quality but a reduction ,in` expense,l through 'the distribution .of the roughing loperations over a roughing or cheaper cutter V.than the nishing cutter.

. A full appreciation of this invention requiresz40f a consideration of the characteristics of a hobbing operation Y and vofl hobbing machines of which` there aretwo general types, referred to in the artas Ydi,iiferential and non-differential machines. yThe former type is exemplified by-such machinesV asv thosefdisclosedY in they patents to Pfauter #640,728 or Waterman #1,364,597;` and thek latter 0rA l10n-,differential type by; the patent to, Eberhardt and, Zimmermann v#1,028,815 or ,Zimmertransmission which operates toproduce three pri-j mary movements, namely the rotation ofthe hobh, the`A rotation orgv continuousA indexing of the. gear blank, and the relative translation or feed between Y thehob and. gear b1ank.,.A1sothe threeA Ydrives 55 Y must be positively nter-connected whereby, during cutting operation, a predetermined relation willbe unvaryingly maintained to result in a gear of uniform and accurate character.

There is, however, a distinctly fundamental difference between differential and non-differential hobbing machines. In the case o f differential hobbers one of. the aforementioned'2 motions of rotation during cutting operation is the resultant of two component motions, one of which,

is derived from the feed drive mechanism. 'Ihese two component motions combinethrough;I a dif;-

ferential mechanism to produce the required re-w sultant rotary motion. The characterslics.v f

such an arrangement are best illustrated` byV noting the effect upon the corresponding rotary, motion when the feed is rendered operative or inoperative. Assuming the machine to have been properly adjusted as to ratios for a particular'hob, and helical pitch on the gear, then with the machine in operation and the feed disconnected the gear will continuously index and the tooth spaces thereof maintain a proper registration with the hob helix. If the feed is then connected the rotation of the hob or gear, as the case may be,

will be continuously modiiied compatibly with thel tempting to establish the initial setting for aY recutting operation of helical gears. In such manipulation with a non-differential machine the `hob cannot be brought manually into any degree of registration with the gearand allowed to rotate with the power feed disconnected without the hob gradually milling intothe'teeth of the helical gear.

An outstanding net result and distinguishing characteristic, therefore, between aA setting operation for re-cuttinghelical gears in a differential machine and in a non-differential machine, and one which renders such operationparticularly difficult in the latter type, resides in the fact that with a differential machine the hob and gear may be positively secured in position and the correct initial relation established through independent manual adjustment of the feed. With a non-differential machine, however, the three drives are so related as to necessitate the simultaneous adjustment of two of the relations to achieve the correct initial setting.

The present invention is particularly advantageous in being applicable to hobbing machines of the non-differential type, and enableshelicoidal gears, which have been previously rough-cut on a machine of whatever type, to be finishedv or recut on such non-differential machine with extreme facility and precision.

is described as achieved with such type machine-.- The apparatus, as depicted in the drawings, in-

" cludes a transmission system capable vof-imparting the proper compatible motions totheehcb and gear blanks. As a primary feature of theV organization the transmission branch: foreii'ecting the relative translation between -thehob=and gear blanks has anelectively separable driving The organizationspecically disclosed herein, therefore,Vv is a nonv differential machine in general and-the methodconnection interposed therein capable of being disconnected to permit of a desired independent linear adjustment between the hob and gear blanks and then re-engaged. The proportioning of the ratios and driving elements, and the arrangement in general is such that the ire-engagementV may be effected without disturbing the previously manually effected setting to any substantial degree, such as would be the case with an ordinary coarse tooth positive clutch, for example. As disclosed the electively separable connection comprises an auxiliary clutch in the transmission line operating to translate the hob carrying head. The clutch itself is fine-toothed and accompanied by a location and proportioning of driving elements such that, if in making the manual set-up the teeth should be displaced the maximum angular distance possible between two adjacent inter-engaging positions, the subsequent engagement will result in but very little displacement of the hob head, and thereby the adjusted relation of the hob with respecty to theV gear blanks. The particularly practical advantage of this isthat` but a minimum amount of material need be left on the roughed out gear blanks for removal in the re-cutting operation.

A further very important and co-related function afforded by the machine organization of this.

invention resides in the provision ofv means, peculiarly effective in the type ofr organization shown, for the removal of back-lash from thedrive trains, thereby eliminating, as far as possible, the indeterminate, but frequently very. se-

rious, departure from the correct relation, should.

an ultimate driven element be delayed in picking up the corresponding motion from a particular transmission branch containing back-lash, whileother motions to the gear blank or hob had been immediately initiated.

The more specific features of the methodand.

description of the drawings, from which it willy be'apparent that the present invention will enable one to re-cut a gear, or a stack of gears, that have been previouslyrroughed on another machine and/ or by some other process. Further, that such operation may be performed in an economical and rapid manner; and that from the close initial setting, which may be originally attained and subsequently maintained through the complete re-cutting operation, but little stock need be left in the roughed-out tooth spaces for removal onthe finishing cut whereby the final tooth form, spacing and finish will satisfactorily comply with present exacting requirements.

The more specific objects and advantages will be indicated in part or rendered apparent from the hereinafter description.

To enable others skilled in the art so `fully to apprehend the underlying features that they may practicethe method and compound a suitable ma chine therefor, in accordance with the; Various. waysv contemplated by this invention, drawings depicting a preferred typical construction have been annexed-as a part of this disclosure and, in.

suchrdrawings, like characters of reference denote corresponding parts throughout all .the views,`

Figure 1 is a general organizational View in.

elevation of a hobbing machine containing an ar.-

taken on the opposite side of the-hobbing ma: chine `from-Fig. l. Fig. 3 is a fragmentary view ooi rying the hob spindle.

depicting in particular the auxiliary fine-tooth clutch contained in the drive to the hob carrying head. Fig. 4 is a front elevationl 'of the 'entire machine. Fig. 5 is a view of the hob slide and uniL versal table carrying the hob spindle. Fig. y6 is a cross sectional View showing details of the 4drive for rotating the hob spindle. Fig. 'l' isa View similar to Fig. 5 but with the'universal table* removed to show better certain details. FigsS and 9 are fragmentary cross-,sectional views'ofr View of certain manual control leversexhibited more generally in the assembly view of Fig.. '11..

The general arrangement of theparticularhobbing machine illustrated-herein is similar to thatf disclosed in my prior Patent #1,625,581and includes a bed B upon Which-is mounted the upright tool support S horizontally adjustable .along the bed on the ways Ill; and a work spindle W supported in large bearings in the bed B. The work spindle occupies a fixed position at the forward end of the machine where it remains conveniently accessible at all times for the application or removal of gear blanks, and kbeing nontranslatable, enables the work spindle to be Very `rigidly mounted in a solid support free from vibration under the` stresses normally 'imposed y f i i3 also carries a short transverse shaft i5 supthereon. y

The stanchionA S is of considerable extent in horizontal cross sectional area providing a large base area contacting with the ways l of the base B providing a very substantial support fully capable of effectively resisting the turning moments resulting from the pressure on the hob while in engagement vwith the work. The stanchien S in turn carries a universal cutter slide or head H translatable on the verticaljways Il on the forward face of the stanchion. The head H includes a supporting bracket l2 which is adapted to be swivelled 0n the base portion I3 of the head and clamped in position through the medium of bolts having their heads engaging in the circular T-slot/ i5 of the base portion` I3. The bracket i2 is provided with a, hob spindle i6 carrying the hob cutter C rotated through mechv anism to be later described in greater detail. Y The power drive for the entire machine vvproceeds from the pulley P adapted, as shownf,.to be must be maintained between the several elements,

is derived from the main shaft Il. An auxiliary and alternative drive for producing independent rapid traverse movements of the head H is pro-A vided through mechanism including the parallel shaft 2| which will be again' referred to and'lde- Y scribed as to detail. l

Three branch transmission lines proceed fromy the main shaft Vl, one for rotating `the workcarrying spindle W; another for rotating the hob spindle; and a Vthird for feeding the head H` oar- Thesecan be most readily observed by referenceV to Fig. 11. The successive elements inthe vwork'rotating branch comprise a gear 22 vonsthe end of shaft Il meshing. with .a gear 23u/nich has integral therewith a bevel gear 24 'matingwith a bevel gear 25 secured on the long shaft As shown at the left in Figs.. l andll the shaftl 2S carries a spur gear 2l which drives a spur gear 28. .A spur gear 2S is formed withlgear 23 torotate therewith and drives a larger gear 3@ fixed on the long shaft 3l.. Al

worm 32 secured, or formed, on shaft 3l drives a worm'gear 33 secured on the lower end of the work spindle thereby completingk the drive for slowly rotating the work spindle W carrying one` or moreblanks W.

The hob rotating transmission will lnext be' described. The stanchion S carries a verticalI splined shaft 36 mounted in an upper bearing B'Land alower bearing 38 in a brackets@ secured .to or formed with the stanchion S. A

gearfsi likewise supported in the bracket 3S is splined on kthe horizontal shaft Zi'and meshes with a bevelgear di secured on the lower end ofthe shaft 36.

This constitutes an adjustable drive for the vertical shaft 3E carried by stan- Y chion S enabling the stanchion to be adjusted along its supporting ways on the base B. Carried in suitablebearings in the baseportion i3 of the slide I-l is a bevel gear 42 splined on the vertical shaft 3S. A shaft t3 (Figs. 5` and 6) supported in vbearings in the-base i3 carries a bevel gear ifi engaging with the bevel gear 42. Y The base ported in bearings 4S and el (Fig. 6). Formed on the shaft t5 or secured thereto is the worm gear 43 meshing with the wormli on the shaft 63. A bevel pinion 50 is also-carried by shaft i5 integral with worm gear 58. End thrust on the shaft i5 is provided for by the ball thrust bearings l and 5?; respectively. The shaft i3 eX- tends through the base i3 to the right as shown e. g. in Figs. 5 and 6.

This outer endis provided with a nut 43e rendered non-rotatable with respect to shaft e3 by locking pin 53h. TheA particular advantage of thisV construction will be subsequently described but for the present it may be noted Vthat it .enables the application ofa wrench. thereto for rotating the drive mechanism backwardly.

' A shaft 55 is carried in suitable bearings in the swivelable bracket l2 including the end ball bearing 5S engaged by and adjustable as to position by thenut-'l. 'Ihis shaft carries a bevel gear 53 at its inner end mating with the bevel gear 56; and .a spur pinion 59 at the outer end engagingwith a larger spur gear E9 secured on the hob cutterspindle to rotate the latter. It will be `observed that the shaft 55, including its gear 5.8,' Yis carried by the swivelable bracket I2 whereas the driving gear 5e is carried Vby the base '13, the axis of the latter being coincident withithe axis of the'bracket I2, thereby enabling the bracket to be readily rotated to vary the direction of they hob axis in accordance with the variable factors of the helix angle of the hob and the gears to be formed.`

IThe 'third transmission line, serving to feed, the hob slide H, proceeds from the long. shaft 3i mounted in the bed. For this purpose a bevel gear 63 secured thereon drives a bevel gear 64 secured on the shaft 65 which shaft is likewise carried in bearings in the bed B. Another short shaft 66 ymounted in the. bed B has a worm gear 61 thereon engaging with the worm 68 on the shaft 65. A` spur pinion 69 on the shaft 66 meshes withA gear 'lllv of an idler gear set which 4a-lower bearing 34. Asleeve 8| prevents movement in the opposite direction. The gear is adapted to be clutched` includes thev gear 1| meshing with'gear '|2r1ixedV on a sleeve I3 rotatably mounted' on the shaft 14; The sleeve 13 is slidable longitudinally of the shaft I4 and may be clutched thereto to drive the shaft through the intermediary of a clutch` S to move therewith and include a bevel gear I8V mounted in a suitable bearing provided by` a` bracket 79 secured to the lower portion of the stanchion. The gear 18' is splined'on the horizontal shaft 'lli thus permitting adjusting of the` stanchion along its ways. A bevel gear 80. mates with gear T8 and has a sleeve extension V8| rotatably mounted on the vertical shaft 82 and in the fixed bearing 83 of the stanchion. End thrust of the gear and sleeve is provided for by Acollar 85 secured to the to the shaft 82 to drive the latter 4through the medium of a fine tooth clutch indicated as a whole at S5, the more specific purpose and details of which will be later described;

The vertical shaft 82 is of considerable length extending to near the top of stanchion S, and has the spur gear 81 secured thereto at that point meshing with a spur gear 88. Gear 88 is mounted in a solid kcross bar 89 of the stanchion S and includes as a unit an internal nut cooperating with the non-rotatable threaded feed shaft 90, the lower end of which shaft is secured at 9| to the slide H. Rotation of the gear and nut 88, therefore, serves to raise or lower the slide H as the oase may be.

Thetransmission just described constitutes the feed for the slide and normally is at a slow rate andfin but a single direction (down). An auxil iary drive is provided, however, adapted to be injected into the train of mechanism as desired to rotate the gear and nut 8S at a more rapid rate, and in either direction, to thereby produce a corresponding rapid traverse of the hcad H either up or down as the case may be. This rapid traverse drive is derived from the gear 4 integral with, or secured to, the pulley P, and is, therefore, independent of the clutch controlled shaft I'I. Gear G4 meshes with gear 95 mounted on shaft 2| carried in the bed A, the opposite end of shaft 2| carrying a. bevel gear 9S engaging with opposed bevel gears 97 and 98 normally freely rotatable on the shaft 'M but adapted to be selec-- tivelyclutched to the shaft 14 through shifting .of

the clutch collar 99 into engagement with the opposed clutch teeth formed on the respective gears 9.7 and 98 complemental to the teeth onthe clutch collar. As will bepointed out more in detail an interlocking control mechanism is provided, whereby clutch 'l5 controlling the slow feed and the clutch S9 controlling the rapid traverse, cannot be made concurrently effective. An impositive drive to the shaft 2| also may be incorporated in the transmission line comprising a friction plate connection between the gear and the shaft 2|, the gear 95 being clamped between plates 95a keyed to the shaft 2|.

A means for moving the slide H manually is also provided comprising ahandwheel H12` carried by shaft |63 mounted in the stanchion S which gear: lbmatingwitha gear |05 secured on the shaft 8'2;V The-manual'adjusting means just described has a particular and important function in' setting; uprthe machine for the recutting of gears,` as-:will be pointed out.

At infrequent times the stanchion S must be adiustedforward or back on its ways as, for example, -When gear blanks of different diameter areto beioperatedy on. A manually operative meansforthis purpose is provided comprising a feedscrew shaft |08, ,one end of which is rotatably securedin a bearing,y |09 in the stanchion S and the opposite end'of4 which threads into a nut l0 fixedin the bed-A.. A cross shaft I mounted in the stanchionS has a4 hand wheel H2. affixed to itsouter end;v and a helicalgear H3 affixed to its inner endwhich gear mates with a companion gearI H4' splinedon the shaft |58. Rotation of hand wheel I2, therefore, will serve to translate the stanchion S along its ways.

The manual-controls for the various clutches and theinterlocking means for preventing incompatible operation thereof to the injury of the machine or work will now be described. The details; thereof are, for the `major part, identical with those illustrated #1,625,581, to which reference may be made for a fuller disclosure as to certain specific details. Inthe interest of convenience, however, the elements, for the most part, willbe described herein. As previously, noted the master clutch within the pulley unit P is controlled from the lever 20. Upward movement oflever 20 in Fig. ll engages the clutch.` `The lever is continuously Urged downward, as shown in this figure, to its declutching position, bya spring pressed plunger ll bearing against a projecting finger i8 rigid with the lever 28. Whenengagement of the clutch is effected, however, a latch H9 secured on the shaft |20. hooks over a second finger i2l, rigid with leverV 2D, and locks Vthe latter in its clutching position. A releasable spring pressed plunger holds-the latch |19, and thereby the lever 2B, in this position until released manually or automatically by partial rotation of shaft |28. Manual rotation of shaft |20 is effected from the hand lever |22 secured thereto; and by automatic means through movement of lever |23, likewiseV secured to the control rodv |20. A rod |24, ex-

tendingY vertically alongside the stanchion S, isV

pivoted to the lever |23. This vertical rod carries anadjustable stop |25 which is adapted to be engaged by dog |26 secured to the slidable head I-I. Such engagement will, through linkage just described, trip the latch ||9 and permit plunger IH to move the master clutch to its disengaged position, thereby determining the limit of downward feed.

The linkage mechanism for operating the rapid traverseclutch sleeve comprises an oscillatable shaft |28 to which is secured a finger 29 projecting into an annular groove in the clutch sleeve; and a bevel gear |38 secured to the opposite end of shaft |28v and meshing with va bevel gear |3| secured.V on an oscillatable shaft |32, to which shaft is also secured oppositely projecting levers |33. and` |34for manual and automatic operation respectively. w

`The automatic feature is operative to move the clutch 99 to neutral at appropriate points in the travelof the head. The mechanism therefor includes, in addition to that just described, a vertically extending rod |35 pivoted to the lever |34-at the lowervendof the rod; and a bell crank sha-ftY at -the` opposite: end'. alsoU carriesv aA bevel |36fpivoted 'to the stanchion S at |31 and having.

one arm pivoted atl |38 to the upper endof rod |35 and the other arm adapted to contact with a l.camplate |39v secured to the translatable head H. In the position of bell crank |36 shown in Fig. 2 the clutch 99 vis in neutral. In addition to cam plate |39 dogs |628 and |4| are provided, adjustablysecured to the vertical rod |35. f

The operation then would be somewhat as follows: Assumingthe head H to be in its normally uppermost position the cam plate |39 would be elevated from the position shown in Fig. 2 and the arm |0112 free from contact therewith. "I'o initiate a downward rapid traverse, the operator would depress the lever |33 engaging the clutch 99 with the appropriate gear; raising'v vertical rod |35; and rotating bell crank |36 clockwise in Fig. 2 to bring arm |38 into thev path of cam plate |39. As the head proceeds. downwardly the inclined edge |43 of the cam plate will engage arm |42 camming the bell crank 38 tor the position of Fig?, and throwing the rapid traverse clutch to neutral. The controls would normally be so adjusted that the hob has approached reasonably close to the work and in positionrfor the initiation of the slow feed. As the slow feed proceedsr the arml M2 continues to ride along the straight edge, |88 of the camplate |39. For rapid Ytraverse reverse the corresponding manual shift- 'ing of clutch 99 will have been moved clockwise a certain angle from the position shown in Fig. 2. The stop will serve asa means to return the clutch to neutral if theV reverse movement v.is allowed to proceed until such stop is engaged by V.plate |26. The stop lell likewise ac ts as an auxiliary safety device to limit'd-ownward rapid traverse.

There is yet to be described the operating and control means to the feed clutch 75. This is ac'- complished through the oscillatable controlv rod |45 .(see Fig. 11) to which yis secured at one end vthe manual lever |56 and at the otherendbevel gear |67 meshing with bevel gear |48 on the con? trol shaft U59.V Theend of shaft |49, adjacent clutch 75, is preferablyy provided with an 'impositive .clutch operating* connection comprising a finger |58 loosely mounted on shaft |49 'and `adapted to'fioat betweenV the projecting ears l5! 1and|52 rigidy withthe shaft |439. Earv |52 carries a spring pressed plunger |53Vadapted to bear against the finger |58. In the event, therefore, lthatthe opposed clutch vteeth are not correctly Ipositioned for instantaneous inter-engagement upon manipulation of lever |45, a delayed lengagement will occur. Preferably also'a detent means "is provided for ensuring complete'movement of y,

the clutch 75 to either extreme position and maintaining it in such position except upon intended Yshifting thereof. Any well known'device for this purpose vmay be employed, such asthat'shown in Ymy Patent` No. 1,625,581 referred to above. Y

As shown in Fig. 12 an interlock is provided for preventing the feed clutch 75 and the rapid traverse clutch 98 being concurrently engaged through inadvertent manipulation or accident. Secured on the control shaft 5 to the feed clutch 75 and'integral with the control lever |48 is the 'projecting nger |55 carrying the V-shaped lug |58. The lever |33 on control rod |32 to the rapid traverse clutch 99 has integral therewith a ledge portion |57 with. which the lug |56 is arranged to cooperate. he ledge is provided with a V- Yshaped depression i523 positioned between the high portions |59 and |88. In the position shown in Fig. 12 lever l' 33 is in mid-position and its rapid traverse clutchvinvneutral. The lever |46, vhowever, has the lug |56 engaged in the depression |58 and the lever |46 is in its lower position wherein feed clutch 75 is in engagement. If lever |33 is moved to either extreme position, as shown in broken lines in Fig. 12, the lug |56 will ride on the cam portion |59 or |89 as the case may beV and lever |45 moved to its upper position, shown in broken lines in Fig. l2, and the .feed clutch 75 accordingly disengaged.

Auniversal cutter slide is incorporated in the vmachine presentingadvantageous features with reference to its manner and range of adjustability and means for`iirmly maintaining it in .adjusted position.r The hobv spindle bracket may be rotated on its base. i3 through an angle of 180 and more, which necessarily satisfies any condi.- 'tion of operation presented by. the various types of gears and thefvariation in the helix angle of the hob and gears. As shown in' Fig. 6 the hob 4spindle supporting bracket I2 is provided with an annular rflange |85l adapted to project' into'a circular` bearing |88 of Vthe base i3. -In additionr ample plane bearing surfaces are provided on the base I3 lagainst ,which corresponding surfaces of the bracket I3 bear forming arigid metal to metal Vcontact when the heretofore mentioned bolts i8, vengaging in the T-slots l5, are drawn up.

Angular adjustment of thebracket i2 Vabout its`aXis is .conveniently accomplished through the "application of a wrench-to the projecting squared end |87 of the Ash'a'ft'lti supported -in bearings |59 and |59a ,of-the bracket l2. Shaft r`|68 carries a worm |70.. which bears at one end againstv a Vcollar |7| vencirclingthe shaft itt, in turn bearing against a washer |72 .supported by the outer bearing sleeve |59 secured in' the bracket |2 by machinefscrews |73. Thrust inthe Vopposite direction and also 'axial adjustment is providedfo'r by the outer collar` |74 threaded on the shaft |8,-,and compound washers |75 and |78 inserted between the collar |75. and bearing sleeveI9.y e Worml |79 meshes with worm gear |77 of the ystub unit `|78 having. the small and large bearving |79 and |80 respectively in the `bracket I2. ,Thefstub .unit |78 .also carries'the small Vspur ,gear-MIB!rrr which. meshesl' in assembled position, withthe ring gear segment 182 Vsecured to the base |3 .co-axial with the shaft 45 as shown particularlyfinFig. 7. Rotationz'of the shaft |88,

therefore, causes Vthejgearlfl to roll around the gear segmentV |821a'nd, tlie`bracl et I3 to be an- Yularly.adjusted 'about its axis in aY corresponding manner.

Suitable graduated',frneans*for` Yindicating the angularlyadjusted position may be provided, comprising, in .the'spec'ific form here shown, a thin arcuatev plate|85 imbedded inthe base i3; and a small plate |88? secured tothe bracket l2 to move adjacent the plate |85, the two having appropriatefindiciato which theangular position of the bracket l2 can bel'referred.

The cutter arbor is vsupported on the frame I2 between theopposed bearing members l|87 'and |88, the former constituting the'l driving end. lEach of these bearing membersisaxially adjustablel to vsuit the particular hob and arbor, the

bearing member |88 being held on its supporting surfaces by cleats |89, and bearing member |87 by cleats |98. Axial adjustment of bearing member |87 is produced through rotation of the nut |9| threaded on and pinned to the shaft |92, the

exact detailsv of .the connection, not beingv of importance tothe present invention, are not shownffhe arbor holder |93] is 'secured to and driven from the shaft |94 splinedrin the'gear Si! which is rotated through the train of mechanism heretofore described.

In .the foregoing description an auxiliary clutch et has been noted in a generalv way. Thisv clutch, it will be seen, is interposed in the drive for translating the hob carrying slide. The peculiarly unique and important` function of this clutch, in its association with the general machine organisation, will now be described, together with certain details of construction.

The clutch 86 may be disconnected, as desired, through the medium of hand lever |95 (FigZ) secured on shaft l'l, the opposite end of which shaft has a lever |98 secured thereto carrying a pin. i tracking in annular groove 290 of the sleeve 291| splined on the shaft 32. To hold the clutch Se in disengaged position a latch 262 is provided having a hook 2&3 adapted to engage under a pin 204 secured in the handle |9.

Fig. l shows a rnodied form of manual clutch operating means in which an eccentric pin 235 is mounted on the shaft 79'| and projects into the annular groove 28d of the clutch sleeve l23|".

As the handle |96 is swung 180 degrees the clutch becomes self-lockingin either engaged, or disengaged position, as the case may be.

With the clutch 85 disconnected the hob carrying slide may'then be raised or lowered by rotation of the hand wheel |02. For a particular purpose, to be described presently, lthe hand wheel |52 carries graduation marks 20,5 on the hub thereof arranged to be referred to the Izero mark 2d? on the fixed supportingl bearing 288.

With the' understanding of the physical embodiment of the invention gained from the above description, its adaptation to the method Yof the invention, and the method itself, will be reviewed `somewhat in detail. Q p

It is assumed that we have a group of helical gear blanks in which the teeth have been roughed out on some conventional machine.. In view of the Yaccuracy of setting, which may be4 initially effected and maintained with the present ma.- chine, the roughing operation may have been carried to the point of bringing the ,gear teeth size and shape very closely to the ultimate finished dimensions. In this respect it may be noted that the best nish and accuracy of spacingA and toothr form is obtainedv when only .O05 to .010 inch of material is required to be removed from the sides of the teeth on the finishing operation. The method of finishing or recutting theseroughed gears then consists, 4in accordance with this` invention, of placing one or a stack of these gear blanks on the work arbor .of the machine illustrated. The gear blanks at .this stage are not clamped on the arbor .but are left free enough to be independently rotated'. It is tol be understood that the machine has 4been provided with the proper hob and that the proper angle forthe hob arbor has ,been established .through adjustment of` the `universal table which, as shown, is of a type to render this readily obtainable and adaptable `to any conditions which.' would be encoun: tered. Also the .required gear ratios to impart compatible motions to the `hob and Agear willhave been established.' f

The initial machine operation, after the gear blanks have been mounted on the arbor, will be to bring the cutter slide downward to locate the cutter closely adjacent the initial cutting position.,` .Thisisaccomplished Of4 Course, through the traverse clutch 9S, the main feed clutchV l5 being at this time disengaged. Feed clutch identical for that purpose.

is then engaged. Following this, hand wheel |02 is rotated backward, i. e. against the normal down feed to take Vup the back-lash between it and the feed clutch which has just been engaged. This reverse rotation` is slight insofar as observable Vmovement is concerned, but is, nevertheless, important in that it removes all back-lash in the feed train and contacts the driving surfaces. The re-setting clutch 85 is then disconnected permitting the `cutter slide to be manually lowered or raised by the hand wheel |02. Through oscillation of the hand wheel the hob is maneuvered into exact registration with the uppermost gear blank teeth. It is to be remembered that the gear blanks are loose on the work spindle and two independent motions are thus permitted. That is, the hob may be vertically translated and the gear blanks rotated. In conjunction with the operation of lowering the hob and oscillating the gear blank, the present method contemplates further means for the achievement of an initially accurate setting and the preservation thereof upon the institution of the power operation. This consists of the step of rotating the hob and its drive mech.- anism in a reverse direction, which may be accomplished, in the particular hob slide construction shown, through the applicationof a wrench to the nut ,|53a on the conveniently projecting end of shaft .43; In practice the same wrench used for the cutter spindle clamping nut may be employed for this operation, these two nuts being made If a reversible gear connection is utilized in place of the gears 48 and 49 such backward operation of the hob and drive mechanism may, in fact, be through application of the wrench to the cutter spindle clamping nut I Sa. VIt will be apparent that this reverse rotation Vof the hob serves to remove all back-lash and to bring all drivng faces into contact in the corresponding ldrive train just as in the case of the feed mechanism to which reference was made above. Accordingly, there is eliminated the factor of delay in picking up the corresponding motion upon the initiation of .the power drive while the other one or more motions had `materially progressed. Accuracy of initial setting is thereby preserved, and danger of broken cutters .or of .damaged gears is obviated, as will perhaps be more apparent from a consideration of the .entire method, the further steps and features of which will now be continued.

'TheY steps thus far related result in the hob teeth being set exactly into the adjacent roughed out helicoidal gear tooth spaces, and the proper three-fold relation between the hob and uppermost gear blank accurately established. If several gear blanks are mounted on-the work arbor, as would usually be the case, the lower ones may be accurately lined up in succession from the uppermost one in engagement with the hob, through the use of a suitable pin or wire in the gear blank tooth spaces, and the stack, as a whole, then firmly clamped in position.

. After the proper registration of the hob and gear blank has been established the re-setting clutch 86 is engaged and the machine is ready to start on its nishing cut. A feature of prime importance, in connection with this clutch and its co-related drive mechanism, should be here noted. This auxiliary electively separable connection between the cutter slide and the normal power drive may assume various forms, an essential characteristic being that of enabling the power .drive to be established Without disturbing the setting of the hob with respect to the gear .stances but it may be noted, in general, that it must be within the allowances of Ymaterial left for.

finishing purposes on the gear blank teeth. In this respect it is further noted that best finishingA results are obtained when but,.005 to '.010 of an inch are removed on the finishing cut. A further essential characteristic of this separabledrive connection is the requirement that the connection, when effected, must constitutev a positive non-slipping drive.V

The mechanism shown'includes the resetting clutch 86 which has been heretofore referred to, somewhat in general; but an important feature thereof, which should now bespeciflcally noted, is that the inter-engaging teeth are closely'arranged constituting what is termed a fine-tooth clutch. The exact spacing and number of teeth may vary, dependent upon circumstances and the `mechanical ratios `between subsequent elements Yin the drive train. A clutch with 24 teeth in conthegear blank to ensure thatthe finishing cut junction with theA gearY ratios and arrangement shown, has been found entirely satisfactory. The number of graduations 266 equal the number of clutch teeth, and the stationary zero line 2M in conjunction with the graduations indicates the Yposition of fthe re-setting clutch-teeth one to another. Also, eachgraduation or one toothV of the clutch is equivalent to .00,5 of an inch in vertical movement of the cutter. Y vv The Vparticular constructionfor this auxiliary electively separable connection, exemplified by the clutch 35, is to be understood as illustrative only, andthe term fine-tooth clutch, as used herein,including the claims, is intended to generically vrefer to a means for disconnecting the 'drive and positively re-establishing the drive at will, the arrangement being such that the re-engagernenty may be effected without: requiring,` in any single instance, more than a small angular adjustment between the complemental members to complete'- ly establish a positive drive therethrough.

With the above comprehensive description" of the construction and function of the rei-setting clutch 86 the further steps constituting the method of re-cuttinghelicoidal gears in its complete aspectV may now be-more conveniently described. Immediately upon the'beginning of the operation under the machine; power, observation should be made to determine whether thehob is cutting uniformly on each side ofthe' teeth.' As has been previously noted, it is desirable that a minimum of materiallbe left for nisl'iing operation ywhich necessitates, however, a Very" closeY adjustment of the hob with respectto the gear. If upon the observation noted it appears'that the hob is not cutting uniformly the next step is to stop the machine; disconnect the're-setting clutch 86; and manually move the cut'terfslide up or down, `as the case may require, paying attention to the amount indicated by the graduations 206. The resetting clutch can then be re-engaged and normal power operation of the machine resumed."

The setting-up operation frequiresfbuta fractionof the time necessary to give an explanation thereof, and can be .accurately accomplished by an ordinarily skilled operator. The fine degree of adjustment available, together with' the capability of the elimination of back-lash, as is possible in the arrangement shown, result in a lnondiiferential hobbing machine capable of ready application to the re-cutting of helicoidal-gears; and-further capable of the production of helicoidal gears of Athe utmost perfection and precision. y l

With' the back-lash removed, through thev means provided, assurancemay be had that the related motions 'of work rotation, hob rotation, and hob translation'will be simultaneously and instantaneously initiated'upon engagement. of the main clutch. The instrumentalities for removing the back-lash, itV will be noted, are connected into the corresponding transmission lines at points near the end thereof. In the case of the feed train e. g. such instrumentalityV is closely adjacent the hob whereby it is effective on the major portion of the transmission line and includes,

in particular, the feed clutch 'l5 subject to considerable wear. Y

These important characteristics of elimination of back-lash and of fine adjustment, as conjointly Vand cooperatively related in the organization shown, lserve to eliminate broken cutters, and

`damaged top gears, while at the Sametime peritting thecutter to be'started -close enough to- `vwith the result that the ultimate gear teeth will possess the perfectionofrproportion, uniformity and vfinish desired. i

Without further analysis, the foregoing will so fully revealthe gist of `this invention that others can, byapplying current knowledge, readily adapt o of this invention and, therefore, such adaptations should be,and areintended tobecompre hended within the' meaning and Yrange of equivalencyof the following claims:-

Having thus revealed. this invention, I claim as new and desire to secure the' following combina;- tions and elements, ory equivalents thereof, by Letlters Patent vof United Stateszv.1. AA non-differential hobbing machine combiningY a rotary Ytool spindle; fa rotary work spindle, saidspindles being relatively translatable to effect a feed; power transmission drive mechanism including branches for rotating said workspindle, rotating saidtool spindle, and for effecting-saidfeed, the drives for said rotary mov tions being unaffected by the drive for effecting i said feed; means for manually rotating said hob `reverselyrtc its power drive to remove back-lash preliminary to a hobbing operation; Va main feed Yclutch in said feed drive; an auxiliary fine-tooth clutch in said feed drive; and manually operative means connected in saidwfeed drive to reversely establish an accurate registration of the hob and gearv preparatory to a hobbingroperation.

2. A non-differential hobbing machine combininga rotary tool spindle;.a rotarywork spindle,

saidspindies being relatively translatable; power transmission drives to said spindles for effecting in timed rel-ation said rotary ymotions and a feeding motion oftranslation; `means for Vmanually rotating said hob reversely to its power drive to re-v move back-lashi'preliminary 'to a hobbing operation; a main feed clutch in said feed drive; an auxiliary fine-tooth' clutch in said feed drive;"and

manually operative meansconnected in saidfeed drive to effect said translatory motion.

3. A hobbingmachine combining a rotary tool spindle; a rotary work spindle, said spindles being relatively translatable; power transmission drives to said spindles for effecting in timed relation said rotary motions and a feeding motion of translation; manually operative means for rotating said ,hob reversely to its power drive; a transmission drive for effecting translation at a rapid traverse rate; a main feed clutch in said feed drive; an auxiliary fine-tooth clutch in said -feed drive; and'manually operative means con- `nected in said feed drive to effectsaid translatory motion.

4. A non-differential hobbing machine combin- :ing a rotary hob spindle; a rotary work spindle,

said spindles being relatively translatable to effect a feed; a transmission drive for rotating said hob spindle; means located in said transmission near the hob end enabling the application at will lof a manual device for operating said hob and its transmission in a direction reverse to the normal power operation; a transmission drive for rotating said work spindle; a transmission drive for ,effecting said feed, said transmission drives being associated for operation in timed relation; a main feed clutch in said feed drive; an auxiliary finetooth re-setting clutch in said feed drive and manually operativemeans connected in said feed drive to reversely operate said feed drive to remove back-lash'with said fine-tooth clutch connected and to independently effect said transla-` .tory motion corresponding to the feed when said fine-tooth clutch is disconnected to initiallyfestablish an accurate registration of the hob and gear preparatory to a hobbing operation.

5. A non-differential gear cutting machine combining a work spindle; a cutter spindle; drive mechanism for rotating said work spindle; drive mechanism for rotating said cutter spindle; means for manually rotating said cutter spindle reversely to the normal drive; mechanism for effecting relative translation between said spindles; a feed clutch in said translatory mechanism; an auxiliary fine-tooth positive clutch in said translating mechanism; and meansfor manually effecting said relative translation when said finetooth clutch is disconnected.

6. A non-differential hobbing Vmachine combining a primary source of power; a work spindle; a cutter spindle one of said spindles being translatable relative to the other; a transmission drive for rotating said work spindle; a transmission drive Yfor rotating said cutter spindle; a transmission drive for effecting said translation, said drives being operable in timed relation; major clutch means for electively connecting or disconnecting the power drive through one of said transmission drives; an auxiliary fine-tooth positive clutch between said major clutch means and the corresponding spindle; and manual means connected in said transmission drive having said l clutches therein between said auxiliary clutch and said corresponding spindle for removing back- 'lash from the correspo-nding transmission when said auxiliary clutch is connected and for manually effecting the corresponding drive when said auxiliary clutch is disconnected.

7. A hobbing machine of the non-differential Vtype provided with means adapting it for re-cut- -ting helicoidal gears combining a rotary work spindle; a rotary hob spindle,'one of said spindles being translatable relative to lthe other; power transmission drives to said spindles foreffecting said'rotar-y and translatory motions in l.timed relation; selective means including a main feed clutch for rendering oneof said drives effective independent of one or more of the other drives; an auxiliary fine-tooth positive clutch means in'said independentlyeffective drive; and a manual means connected in said last named drive and associated with said ne-toothed clutch for manually operating the corresponding drive.

8. A hobbing machine for re-cutting rough-cut helicoidal gears combining a rotary tool spindle; a rotary work spindle, said spindles being relatively translatable; associated power transmission drives to said spindles of the non-differential type for effecting in timed relation said rotary and translatory motions; positively engageable clutch means selectively operable for connecting or disconnecting said power translating drive from the other drives, said power translatory drive being associated with said other drives in such manner that the latter are unaffected in their rotary motion by the connection or disconnection of said translatory drive; and manually voperative means Afor effecting a translatory adjustment when said power drive therefor is disconnected, said clutch means being constructed and the arrangement being such that said power drive may be re-established after said manual adjustment Without disturbing the translatory position more than a few thousandths of an inch.`

9. A hobbing machine adapted for nish cutting previously rough-cuthelicoidal gears combining a rotary tool spindle; a rotary work spindle, said spindles being relatively translatable; a nondifferential power transmission means including drives to said spindles foreffecting in timed relaton the'rotations of said spindles and the relative translation thereof; the drives for said rotary `motions being unaffected bysaid drive for producingv relative translation; an auxiliary fineltooth positive clutch in said translating drive;

` inch or less.

10. A hobbing machine ofthe non-differential type adapted to finish-cut previously rough-cut helicoidal gearsv combining a rotary tool spindle; a rotary work spindle, said spindles being relatively translatable; power transmission drives to L said spindlesfor effecting in timed relation said rotary motions and a feeding motion of translation; a main feed clutchoin said feed drive; anauxiliary fine-tooth clutch in said feed drive between said main clutch and the corresponding spindle; manualfeeding means between said netooth clutch and said corresponding spindle, said manual means being effective for removing backlash from the feed drive including said main clutch when said fine-toothed clutch is engaged,

and effective for adjusting the hob into close registration with the gear when said fine-tooth clutch is disengaged.

11. A non-differential hobbing machine combining a rotary work spindle; a rotary hob spin- `dle, one of said spindles being mounted for translation with respect to 'the other; a transmission -drive for rotating said hob spindle; manually operable'means for reversely rotating said hob spindle preliminary to .a hobbing operation to remove back-lash; a transmission drive for rotating said work spindle; a transmission drive for feeding said translatable spindle, said drives being associated for operation in positive timed relation but the drives for said rotary motions being unaffected in their timed relation to each other by said feed drive; a transmission means for independently translating said translatable spindle at a rapid traverse rate; a fine-tooth clutch in said feed transmission positioned therein near the spindle end of the transmission; and a manual operating means for said feed connected in said feed transmission between said fine-tooth clutch and the corresponding spindle for closely adjusting the relative positions of the hob and gear with respect to each other, said manual means enabling the operator to remove back-lash from said feed transmission when said clutch is engaged, and said fine-tooth clutch and the arrangement enabling the power feed drive to be established after said adjustment without departure from the pre-established relation with respect to said rotary drives within the limits permitted by material for a thin finishing cut.

12. A hobbing machine adapted for finish cutting previously rough-cut helicoidal gears combining a rotary hob spindle; a rotary work spindle provided with means for clamping a gear blank thereon; means for effecting a relative feed between said spindles; transmission drive trains for each of said spindles and for Said feeding operation; main feed clutch means for said feed train; an auxiliary fine-tooth resetting clutch in said feed train between said main feed clutch means and the termination of said feed train; means for manually operating said feed train in a direction reverse to the normal power drive from a point near its termination when the machine is idle to thereby remove back-lash; means for manually disconnecting said fine-tooth re-setting clutch, said manually operative feed means being thereby rendered available for independent manual adjustment whereby a closely adjusted initial registration of the hob and gear blank may be effected preliminary to the automatic cutting operation; and means for automatically driving said transmission drive trains at compatible speeds.

13. A hobbing machine adapted for finish cutting previously rough-cut helicoidal gears combining a rotary hob spindle; a rotary work spindle provided with means for clamping a gear blank thereon, said hob spindle being mounted for translation relative to said work spindle;

transmission drive trains for rotating each of said spindles; a transmission drive train for translating said hob to effect a feed; means for automatically driving said transmission trains at compatible speeds for a cutting operation; a main feed clutch means; an auxiliary fine-tooth re-setting clutch in said feed train near its termination; means in said feed train for manually effecting a translation of said hob when said re-setting clutch is disengaged and permitting manual operation in the reverse direction to remove backlash from said feed train when said re-setting clutch is engaged; and means for manually disconnecting said fine-tooth re-setting clutch after the back-lash has been removed from said feed train to permit thereafter the manual feeding of said hob whereby a closely adjusted registration of said hob and gear blank may be effected preliminary to the initiation of the automatic cutting operation, said fine-tooth clutch permitting re-establishment of the feed drive for automatic operation without material disturbance of the previous setting consistent with the allowance o! metal on the gear blank for a re-cutting operation.

14. A hobbing machine adapted for finish cutting previously rough-cut gear blanks combining a rotary hob spindle; a rotary work spindle provided with means for clamping a gear blank thereon; means for mounting one of said spindles for translatory feeding movement relative to the other; a transmission drive train foreach of said rotary spindles, and for said feeding movement; means for automatically driving said transmission trains at compatible speeds; a main feed clutch in said feed transmission; an auxiliary line-tooth re-setting clutch in said feed transmission; means for manually operating said feed train in a reverse direction from a point near its termination, said manual operating means affording means for removing back lash in said feed train when said re-setting clutch is in engagement; and means for manually disconnecting said auxiliary re-setting clutch after the back-lash has been removed from the feed train to permit manual feeding whereby a closely adjusted registration of the hob and gear blank may be effected preliminary to the cutting operation, said fine-tooth clutch enabling reconnection of the feed drive for automatic cutting operation without disturbance of the initial manual setting beyond the close a1- lowance of material on the gear teeth for a finishing operation.

WILLIAM F. ZIMMERMANN. 

